1. Field of the Disclosure
The invention relates to the technical field of wastewater treatment, and in particular to a filler for wastewater treatment and its formation.
2. Description of the Related Art
In 1970s, iron filings and coke were first mixed together to provide a micro-electrolysis filler for the treatment of printing and dyeing wastewater by Soviet researchers. This technology was introduced to china in 1980s. In recent 30 years, it has been applied in wastewater treatment of printing and dyeing, chemical industry, electroplating, pharmaceuticals, oilfield and the like as a result of its properties of simple process, low processing costs and excellent decoloring effect, and particularly with obvious advantages compared with other processes in the aspect of treating wastewater with high salinity, high COD and high-chroma.
However, the conventional iron-carbon micro-electrolysis technology may have many problems. For this technology, a passive film formed on the surface of the iron-carbon filler during the operation may affect the reaction. Generally, after 1 to 3 months, there is a dramatic drop of processing efficiency, the lifetime of the filler is very short, which restricts its application and promotion. Moreover, it is also an important cause of low processing efficiency (removal ratio of COD is 15-30%) of the conventional techniques that the effective contact area between filler and wastewater is reduced as a result of agglomeration and channeling which is apt to occur for conventional iron-carbon filler. Another issue affecting its promotion is that the conventional iron-carbon filler also produces large amount of scraped iron cement which may have negative influence to the surrounding environment. The most important issue is that the traditional iron carbon micro-electrolysis is deeply influenced by the application environment, and generally requires acidity regulation treatment, while the treating effect is not so obvious for quite a lot of toxic organic.
All existing processes of wastewater treatment, including iron-carbon micro-electrolysis, take the way of oxidating the pollutants in wastewater into non-toxic and harmless products. However a large number of nitro aromatic hydrocarbon compounds, azo compounds, halogenated hydrocarbon compounds and toxic and harmful heavy metals exist in the refractory wastewater such as printing and dyeing wastewater, pharmaceutical wastewater, chemical industry wastewater and pesticide wastewater. These compounds and metals described above are rich in molecular structures of double bonds, carbon double bonds, strongly electron-withdrawing groups, azo bonds, benzene rings and the like, which are difficult to be oxidized, but apt to be reduced, and the toxicity and inhibition of the reduction products to microorganisms are greatly weaken, while the biodegradability increases. For example, chlorohydrocarbon can be dechlorinated by reduction, and nitrobenzene can be degradated to be less toxic hydroxyl aniline by reduction.
If the pollutants in refractory wastewater described above can be initially decomposed by treating with reduction technology, the biodegradability of the wastewater may be greatly improved, and it is beneficial to the improvement of the efficiency of the wastewater biochemical treatment. As described so far, researches have been rarely made in this area, and technologies are not yet mature.